If it does not occur in previous versions of Windows, it's pretty obvious that it's a Windows bug.
I doubt that anyone is keen on working around new Windows issues everytime Microsoft releases an update. A demand like "This should be fixed in OpenTTD" is unlikely to encourage the devs or contributors - it's more likely to achieve the opposite by making a post look ... (how do I politely say "childish"?) ... clueless and therefore safe to ignore. Just FYI - and this is my impression as a (admittedly minor) contributor.
@lewisd: sorry about the late reply, I didn't have a lot of useful ideas, like everyone else apparently. I don't want to suggest rolling back to a previous version (the newer version might have some stuff you want, and then there are those security fixes that people tend to ignore until it's too late) or using a virtual machine (probably not worth the hassle), soo ...
- have you tried messing with the settings in the compatibility tab of openttd.exe's properties? Admin privileges, 256 colors, or 640x480 resolution won't help, but perhaps something else will. The second one of the threads I linked in my previous post mentioned disabling DPI scaling which apparently helped for someone back then (must have been on Win8 though). I later suggested that in the third one, but it didn't help, so that appears to be an unreliable workaround.
- the other suggestion I have may be a bit undesirable - scroll the map another way. Arrow keys, cursor at screen edge, the scrollwheel (if you set it to scroll the map; could be useful on mice with horizontal scrolling abilites, e.g. a tiltable scrollwheel), or combining zoom (i.e. the other choice for the scrollwheel) with mouse movement (zoom out, move mouse, zoom in; OpenTTD tries to keep the same tile under the cursor while zooming, so you essentially zoom out to a kind of overview and zoom in on another spot). I see you have discovered left-click scrolling already, and your comment about its limitations is valid (though I think a patch to reduce these would be possible); finally there's a hotkey (default C, I believe) to re-center a viewport on the tile the mouse cursor points to.
I agree that it's not ideal, but I'm afraid I'm out of ideas.The arrow keys are worth trying at least for this reason: They ought to be immune to most mouse problems the operating system can throw at OpenTTD, so if that's accelerating and braking erratically, then the reason may be insufficient bandwidth to push graphics changes to the graphics card (scrolling changes a lot of screen space per frame, after all). That may be sound paradox with today's powerful graphics cards, but they focus on 3D processing power, leaving the old 2D functions in a "who cares about performance, we only need it for historical reasons" state - except there's OpenTTD wanting to use them. Even assuming your hardware didn't change from the point at which it worked properly, the drivers may have changed, which can affect performance.